IMPLEMENTATION OF BIORETENTION SYSTEMS: A WISCONSIN CASE STUDY1

ABSTRACT: The implementation of various bioretention systems was analyzed, including rain gardens, vegetated swales, trenches, and infiltration basins in the St. Francis subdivision, Cross Plains, Wisconsin. Through the examination of archival data and interviews with key participants, it was found that although regulatory and political pressures encouraged the inclusion of bioretention, current standards for storm water management prevailed. The developers had to meet both existing requirements and anticipated rules requiring infiltration. As a result, bioretention systems simply supplemented, rather than replaced, traditional storm water practices. The confusion surrounding dual standards contributed to substantial delays in the negotiations among relevant stakeholders in the watershed. It is concluded that the St. Francis subdivision serves as both a cautionary tale and a bioretention success story. As a caution, this situation demonstrates the need for careful review and refinement of existing storm water ordinances to incorporate water quality improvement technologies, such as bioretention. The demonstrated success of the St. Francis development, however, is that it became a positive prototype for best management storm water practices elsewhere in the region. In addition, the water quality monitoring data from the site has contributed to development of a new county ordinance, the first in Wisconsin to address both quantity and quality of storm water runoff.     

前郭灌区水稻籽粒重金属含量特征及风险评价

于2008年秋季,在第二松花江(二松)下游的前郭灌区内,采集具有不同灌溉史水田的水稻籽粒样品23个,测定稻米和稻壳中Hg、Cd、Cu、Zn、Ni和Cr的含量,讨论了重金属累积特征,并分别采用单项污染指数法和内梅罗综合污染指数法对稻米重金属含量水平进行了风险评价.结果表明,灌溉史越长的水田稻米中Hg含量越高,而稻米中Cd、Cu、Zn、Ni和Cr的含量与水田灌溉史的关系不明显.稻米与稻壳中重金属含量顺序基本一致.Zn在稻米中的含量高于稻壳,其余重金属在稻壳中的含量高于稻米.单项污染指数法评价结果显示仅有1例稻米样品Ni含量超过国家标准含量限值.稻米样品重金属内梅罗综合污染指数为0.33~0.91,平均值为0.51,总体处于安全级水平.通过对稻米重金属的研究发现,长期提取二松江水灌溉导致水田稻米中Hg出现累积,但其累积水平很低,未构成生态风险.以二松为主要水源的哈达山水库建成后,通过灌溉对当地粮食安全造成的影响也较低.     

Flow and mass balance analysis of eco-bio infiltration system

A structured stormwater infiltration system was developed and constructed at a university campus and monitoring of storm events was performed during a one-year operation period. The flow and pollutant mass balances were analyzed and the overall efficiency of the system was assessed. While significant positive correlations were observed among rainfall, runoff and discharge volume (R²= 0.93-0.99; p<0.05), there was no significant correlations existed between rainfall, runoff, discharge volume and pollutant load. The system was more effective in reducing the runoff volume by more than 50% for small storm events but the difference between the runoff and discharge volume was significant even with rainfall greater than 10 mm. Results showed that the pollutant reduction rates were higher compared to the runoff volume reduction. Average pollutant reduction rates were in the range of 72% to 90% with coefficient of variation between 0.10 and 0.46. Comparable with runoff reduction, the system was more effective in reducing the pollutant load for small storm events, in the range of 80% to 100% for rainfall between 0 and 10 mm; while 65% to 80% for rainfall between 10 and 20 mm. Among the pollutant parameters, particulate matters was highly reduced by the system achieving only a maximum of 25% discharge load even after the entire runoff was completely discharged. The findings have proven the capability of the system as a tool in stormwater management achieving both flow reduction and water quality improvement.     

Evaluation of an Infiltration Best Management Practice Utilizing Pervious Concrete1

Abstract: A pervious concrete infiltration basin was installed on the campus of Villanova University in August 2002. A study was undertaken to determine what contaminants, if any, were introduced to the soils underlying the site as a result of this best management practice (BMP). The average infiltration rate at the site is approximately 10^?4 cm/s. The drainage area (5,208 m²) consists of grassy surfaces (36%), standard concrete/asphalt (30%), and roof surfaces (30%) that directly connect to the infiltration beds via downspouts and storm sewers. Composite samples of infiltrated stormwater were collected from the vadose zone using soil moisture suction devices. Discrete samples were collected from a port within an infiltration bed and a downspout from a roof surface. Samples from 17 storms were analyzed for pH, conductivity, and concentrations of suspended solids, dissolved solids, chloride, copper, and total nitrogen. Copper and chloride were the two constituents of concern at this site. Copper was introduced to the system from the roof, while chloride was introduced from deicing practices. Copper was not found in porewater beneath 0.3 m and the chloride was not significant enough to impact the ground water. This research indicates that with proper siting, an infiltration BMP will not adversely impact the ground water.     

Locating Existing Best Management Practices Within a Watershed: The Value of Multiple Methods

There is an increasing need to document the impacts of conservation‐related best management practices (BMPs) on water quality within a watershed. However, this impact analysis depends upon accurate geospatial locations of existing practices, which are difficult to obtain. This study demonstrates and evaluates three different methods for obtaining geospatial information for BMPs. This study was focused on the Eagle Creek Watershed, a mixed use watershed in central Indiana. We obtained geospatial information for BMPs through government records, producer interviews, and remote‐sensing aerial photo interpretation. Aerial photos were also used to validate the government records and producer interviews. This study shows the variation in results obtained from the three sources of information as well as the benefits and drawbacks of each method. Using only one method for obtaining BMP information can be incomplete, and this study demonstrates how multiple methods can be used for the most accurate picture.     

城市环境质量的竞争性评价模型

城市化进程推动了经济的快速发展但也给城市环境质量带来了严重的挑战。为了推动城市环境保护工作,每年全国各地都对城市环境综合整治进行定量考核。首先分析了现有环境综合整治考核办法的不足,阐述建立竞争性评价模型的必要性。竞争性评价模型在指标集的取值范围内选取最优值建立一个虚拟最优城市,以虚拟最优城市为参照,引入优越指数概念,得出待评价城市的优越指数值,然后进行排序和评价。根据该模型对2004年全国18个计划单列市和重点城市的环境质量进行了综合评价,得到了合适的结果;最后总结了模型的特点及以后改进的方向。     

Land Use and Climate Variability Amplify Carbon,Nutrient, and Contaminant Pulses: A Review with Management Implications

Nonpoint source pollution from agriculture and urbanization is increasing globally at the same time climate extremes have increased in frequency and intensity. We review >200 studies of hydrologic and gaseous fluxes and show how the interaction between land use and climate variability alters magnitude and frequency of carbon, nutrient, and greenhouse gas pulses in watersheds. Agricultural and urban watersheds respond similarly to climate variability due to headwater alteration and loss of ecosystem services to buffer runoff and temperature changes. Organic carbon concentrations/exports increase and organic carbon quality changes with runoff. Nitrogen and phosphorus exports increase during floods (sometimes by an order of magnitude) and decrease during droughts. Relationships between annual runoff and nitrogen and phosphorus exports differ across land use. CH₄ and N₂O pulses in riparian zones/floodplains predominantly increase with: flooding, warming, low oxygen, nutrient enrichment, and organic carbon. CH₄, N₂O, and CO₂ pulses in streams/rivers increase due to similar factors but effects of floods are less known compared to base flow/droughts. Emerging questions include: (1) What factors influence lag times of contaminant pulses in response to extreme events? (2) What drives resistance/resilience to hydrologic and gaseous pulses? We conclude with eight recommendations for managing watershed pulses in response to interactive effects of land use and climate change.     

Thermal Pollution Mitigation in Cold Water Stream Watersheds Using Bioretention

This study examines the use of bioretention as a strategy to reduce the thermal impact associated with urban stormwater runoff in developing cold water stream watersheds. Temperature and flow data were collected during 10 controlled runs at a bioretention facility located in Blacksburg, Virginia. It was determined that bioretention has the ability to reduce the temperature of thermally charged stormwater runoff received from an asphalt surface. Significant reductions in peak and average temperatures (p < 0.001) were observed. However, this facility was unable to consistently reduce the temperature below the threshold for natural trout waters in Virginia. The ability of bioretention to reduce runoff volume and peak flow rate also serves to reduce the hydrothermal impact. An average thermal pollution reduction of nearly 37 MJ/m³ was calculated using an adopted threshold temperature of 20°C. Based on the results of this study, it was concluded that properly designed bioretention systems have the capability to reduce the thermal impact of urban stormwater runoff on cold water stream ecosystems.     

农业面源污染现状与防治进展

通过对国内外农业面源污染研究资料的分析,认为农业面源污染的形式主要有:化肥污染、农药污染、农膜污染、秸秆燃烧污染、养殖业污染及水土流失等。农业面源污染导致了土地退化,在全世界不同程度退化的12亿hm2耕地中,约12%由农业面源污染引起;是河流和湖泊的重要污染源,导致美国40%的河流和湖泊水质不合格;是引起地表水氮、磷富营养化的主要因素,欧洲国家由农业面源污染排放的磷为地表水污染总负荷的24%-71%;中国的农业面源污染造成的水体氮、磷富营养化也显著超过来自城市的生活点源污染和工业点源污染。提出目前比较好的防治措施有:最佳农田管理措施、植被过滤带和人工湿地。建议我国控制农业面源污染必须从政策和法律上对农业生产活动进行规范,采用先进的理论和技术实行源头控制,并辅助以过程控制和末端控制。     

第二松花江中下游水体中苯系物含量及分布特征

本次研究采用气质联用仪分析第二松花江中下游江段底泥和水中苯、甲苯、乙苯和二甲苯的含量,并对其分布特征和成因进行了讨论。研究发现,水中苯系物含量均远低于我国地表水环境质量标准和美国国家一级饮用水标准的限值。与国内其他水体相比,第二松花江江水中苯系物含量水平较低。底泥中苯系物含量显著高于水中,市区江段水和底泥中苯系物含量普遍高于非市区江段。